Dear Harry,

>  Was the existence of  Śaṅkarācārya and/or his writings known in 10th century Kashmir?

To my knowledge, Śaṅkara played no role in Kashmir at that time. Maṇḍanamiśra was seen as the representative of Advaita Vedānta. Significantly, the Mokṣopāya addresses and quotes Maṇḍana's theory of error (khyāti [Vibhramaviveka]) in Mokṣopāya VI.325.1–10 (the current volume), adopting "Vasiṣṭha's" inclusivistic approach by redefining the ātmakhyāti of the Yogācāra school in his own terms. As so often, he tells a parable to illustrate his point  (śilopākhyāna, VI.32511–40).

Regards,

Walter